This is the 'busday_count' function exposed for calling from Python.
Make sure only one of the weekmask/holidays and busdaycal is supplied
Indicate that the holidays weren't allocated by us
Copy the private normalized weekmask/holidays data
Fix up the weekmask from the uninitialized signal value to a proper default.
Count the number of business days in a week
The holidays list must be normalized before using it
Make 'dates_begin' into an array
Use the datetime dtype with generic units so it fills it in
This steals the datetime_dtype reference
Make 'dates_end' into an array
Use the datetime dtype with generic units so it fills it in
This steals the datetime_dtype reference
Make sure 'out' is an array if it's provided